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// SPDX-License-Identifier: MPL-2.0
// (c) Hare authors <https://harelang.org>
use format::elf;
use linux;
use types::c;
let ehdr: nullable *elf::header64 = null;
fn sys_infoehdr() nullable *elf::header64 = {
static let ehdr_checked = false;
if (ehdr_checked) {
return ehdr;
};
ehdr_checked = true;
for (let i = 0; linux::auxv[i].a_type != 0; i += 1) {
if (linux::auxv[i].a_type != elf::at::SYSINFO_EHDR)
continue;
ehdr = linux::auxv[i].a_val: uintptr: *elf::header64;
return ehdr;
};
return null;
};
type vdso_ctx = struct {
segbase: uintptr,
stringtab: *c::char,
symtab: *[*]elf::sym64,
hashhdr: *elf::hashhdr,
versym: nullable *[*]u16,
verdef: nullable *elf::verdef64,
};
let ctx: nullable *vdso_ctx = null;
@fini fn ctx() void = free(ctx);
fn get_vdso_ctx() nullable *vdso_ctx = {
static let vdso_checked = false;
if (vdso_checked) {
return ctx;
};
vdso_checked = true;
const eh = match (sys_infoehdr()) {
case null =>
return null;
case let x: *elf::header64 =>
yield x;
};
const ehui = eh: uintptr;
let phui = ehui + eh.e_phoff: uintptr;
let dynvec: nullable *[*]elf::dyn64 = null;
let baseseg: nullable *opaque = null;
for (let i: u16 = 0; i < eh.e_phnum; i += 1) {
const ph = phui: *elf::phdr64;
switch (ph.p_type) {
case elf::pt::LOAD =>
baseseg = (ehui +
ph.p_offset: uintptr -
ph.p_vaddr: uintptr): nullable *opaque;
case elf::pt::DYNAMIC =>
dynvec = (ehui +
ph.p_offset: uintptr): *[*]elf::dyn64;
case => void;
};
phui += eh.e_phentsize: uintptr;
};
if (dynvec == null || baseseg == null) {
return null;
};
const dynv = dynvec: *[*]elf::dyn64;
let segbase = baseseg: uintptr;
let stringtab: nullable *c::char = null;
let symtab: nullable *[*]elf::sym64 = null;
let hashhdr: nullable *elf::hashhdr = null;
let versym: nullable *[*]u16 = null;
let verdef: nullable *elf::verdef64 = null;
for (let i = 0; dynv[i].d_tag != elf::dt::NULL; i += 1) {
const tabptr = (segbase + dynv[i].d_val: uintptr): *opaque;
switch (dynv[i].d_tag) {
case elf::dt::STRTAB =>
stringtab = tabptr: *c::char;
case elf::dt::SYMTAB =>
symtab = tabptr: *[*]elf::sym64;
case elf::dt::HASH =>
hashhdr = tabptr: *elf::hashhdr;
case elf::dt::VERSYM =>
versym = tabptr: *[*]u16;
case elf::dt::VERDEF =>
verdef = tabptr: *elf::verdef64;
case =>
continue;
};
};
if (stringtab == null || symtab == null || hashhdr == null) {
return null;
};
if (verdef == null) {
versym = null;
};
// TODO: use a static variable here somehow(?)
const vctx = alloc(vdso_ctx {
segbase = segbase,
stringtab = stringtab: *c::char,
symtab = symtab: *[*]elf::sym64,
hashhdr = hashhdr: *elf::hashhdr,
verdef = verdef,
versym = versym,
})!;
ctx = vctx;
return ctx;
};
fn vdso_checkver(ctx: *vdso_ctx, version: str, num: u32) bool = {
let prev = null: *elf::verdef64;
let cur = match (ctx.verdef) {
case null =>
return true;
case let vd: *elf::verdef64 =>
yield vd;
};
const versym = match (ctx.versym) {
case null =>
return true;
case let vs: *[*]u16 =>
yield vs[num] & 0x7ff;
};
for (cur != prev) {
if (cur.vd_flags & elf::ver_flg::BASE: u16 == 0 &&
cur.vd_ndx & 0x7fff == versym) {
const aux = (cur: uintptr +
cur.vd_aux: uintptr): *elf::verdaux64;
const name = ctx.stringtab: uintptr +
aux.vda_name: uintptr;
return version == c::tostr(name: *c::char)!;
};
prev = cur;
cur = (cur: uintptr + cur.vd_next: uintptr): *elf::verdef64;
};
return false;
};
export fn getsym(symname: str, symver: str) nullable *opaque = {
const ctx = match (get_vdso_ctx()) {
case null =>
return null;
case let x: *vdso_ctx =>
yield x;
};
const sym_types = (1 << elf::stt::NOTYPE |
1 << elf::stt::OBJECT |
1 << elf::stt::FUNC |
1 << elf::stt::COMMON): size;
const sym_binds = (1 << elf::stb::GLOBAL |
1 << elf::stb::WEAK): size;
for (let i = 0u32; i < ctx.hashhdr.nchain; i += 1) {
const sym = ctx.symtab[i];
const symtype = 1 << (sym.st_info & 0xf): size;
const symbind = 1 << (sym.st_info >> 4): size;
if (symtype & sym_types == 0 || symbind & sym_binds == 0 ||
sym.st_shndx == 0) {
continue;
};
const name = ctx.stringtab: uintptr + sym.st_name: uintptr;
const s: str = c::tostr(name: *const c::char)!;
if (s != symname)
continue;
if (!vdso_checkver(ctx, symver, i))
continue;
return (ctx.segbase + sym.st_value: uintptr): *opaque;
};
return null;
};
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